feat: 增加共享 Agent Browser 调试能力

需求：在 AI 编程会话中让用户与 Agent 共享同一浏览器页面，并查看控制台与网络信息。

实现：新增沙箱浏览器内核、Host API/渲染器面板、OpenCode 工具接入及安全边界测试。

electron/main/ipc/host-api-proxy.ts

@@ -1,6 +1,10 @@
 import { ipcMain } from 'electron';
 import { getPort } from '../../utils/config';
 import { getHostApiToken } from '../../api/server';
+import {
+  getRendererCapability,
+  RENDERER_CAPABILITY_HEADER,
+} from '../../api/renderer-capability';
 
 type HostApiFetchRequest = {
   path: string;
@@ -28,6 +32,7 @@ export function registerHostApiProxyHandlers(): void {
       const headers: Record<string, string> = { ...(request.headers || {}) };
       // Inject the per-session auth token so the Host API server accepts this request.
       headers['Authorization'] = `Bearer ${getHostApiToken()}`;
+      headers[RENDERER_CAPABILITY_HEADER] = getRendererCapability();
       let body: string | undefined;
 
       if (request.body !== undefined && request.body !== null) {